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Marantz 500 Restoration, Here we go...

Well this bad boy is running! I'm done for the night so ill post the details tomorrow but with the SOA pots in their original position I got 284 watts per channel both channels driven before the B channel started clipping. The service manual says to drive the amp into clipping, 55v to 60v before adjusting... Why does this make me nervous? Must be the sound of those outputs singing!
 
So iv'e been listening to this amp for a couple days now and it sounds great. The noise floor is silent and imaging is great. I had a issue with the right meter sticking so I pulled one from another 500 I have for now. Turns out the meter housing was broken and a bad repair was attempted. The new meter dialed in perfectly. The max output I got was 305 watts per channel!
So just about everything was replaced with the exception of the MZ2361 and SZ51066 diodes on the heat sink. The FH1100 diodes on the driver boards stayed too. These were all good and I didnt want to chance going into thermal runaway from experimenting.

So after changing all the TO-39's the bias was out again as expected but since I matched every transistor on the boards I was able to get all four test points within 3 mV of eachother. The original measurements before I started I was able to get the pairs close but they were over 50mV difference from Pair 1 to Pair 2, If that makes sense.

I really flexed this guy while bench testing and though my 300 watt resistors were almost smoking, the amp tube was just as cool as idle! Pretty stable.

I have the rack handles, just waiting for them to get here. This bad boy is good for another 40 years!

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Now THAT'S a WOW moment.

Great job and I wish I was there to hear it.

Keep posting how it sounds. Even thou that really is silly I STILL enjoy reading about how something sounds?????
 
Awesome job, congratulations on restoring this one of a kind unit. Ok other model 500 owners you now know who can restore your units!!!
 
Looks great! I have a question about the "power" line of Marantz amps. I've only owned 22?? style receivers and have never used a pre-amp. I know there are inputs on the back of my 2270 and maybe my 2285. Is this what the 500 power amps are designed for? And if so, would the WPC only be whatever pre-amp is connected or does it combine both? I'm guessing only the power amp, but have never asked!

Mark
 
markpilk said:
Looks great! I have a question about the "power" line of Marantz amps. I've only owned 22?? style receivers and have never used a pre-amp. I know there are inputs on the back of my 2270 and maybe my 2285. Is this what the 500 power amps are designed for? And if so, would the WPC only be whatever pre-amp is connected or does it combine both? I'm guessing only the power amp, but have never asked!

Mark
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Yes, the 500 would need a preamp. The pre out jacks your 2270 and 2285 would serve the same function giving you tone, balance and volume control. The output power of the amplifier is determined by the voltage applied to the input. The 500 has an input sensitivity of 2.25v. So when that voltage is applied to the input via your preamp, the amp will produce its full rated power with the gain controls at max.
 
image.jpg I have been trying to get the fan apart like you did, I removed the snap ring and metal disc but can’t get any farther, any help would be greatly appreciated.
Terry
 
rBuckner said:
Just checked back in on this rebuild. Great work Sal! I mean really great!! :thumbsup::thumbsup::thumbsup:
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Thanks! I’ve had a few more and here and did an A/B comparison with a 510mr I recently finished. The 500 takes the cake in my opinion.

And yea, I ended up replacing the fans. The new ones are cheap and much quieter.
 
For anyone who might be interested, I successfully replaced the original heatsink diodes (Mz2361 and Sz51066k) with 1n4148. The channel with the replaced diodes measures exactly the same as with the original diodes. Thermal stability and bias are perfect.
 
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